package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSON;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient
{
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit)
    {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit)
    {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));

        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //缓存穿透
    public <R,ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit)
    {
        String key = keyPrefix + id;

        //1.从redis中读取缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isNotBlank(json))
        {
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }

        //判断redis命中的值是否是为了防止缓存穿透设置的空值
        if(json != null)    //即shopJson是空值
        {
            return null;
        }

        //4.不存在，查询数据库
        R r = dbFallback.apply(id);

        //5.判断数据库中是否存在，不存在直接返回错误
        if(r == null)
        {
            //为防止缓存穿透，设置一个空值在redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //6.存在，把该数据写入redis
        this.set(key,r,time,unit);

        //7.返回
        return r;
    }

    //创建一个线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //基于逻辑过期防止缓存击穿
    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit)
    {
        String key = keyPrefix + id;

        //1.从redis中读取缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isBlank(json))
        {
            //3.不存在，直接返回空
            return null;
        }

        //4.命中，先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json,RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();

        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now()))
        {
            //5.1未过期，直接返回店铺信息
            return r;
        }

        //5.2过期，需要缓存重建
        //6。缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);

        //6.2判断获取锁是否成功
        if(isLock)
        {
            //6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try
                {
                    //查询数据库
                    R r1 = dbFallback.apply(id);

                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);
                }
                catch (Exception e)
                {
                    throw new RuntimeException(e);
                }
                finally
                {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }

        //6.4返回已过期的店铺信息
        return r;
    }

    //获取锁
    private boolean tryLock(String key)
    {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    //释放锁
    private void unLock(String key)
    {
        stringRedisTemplate.delete(key);
    }

}
